1. Field of the Invention
The present invention relates to boiler optimization in heating plants which have more than one boiler available for use. Typically, in multiple boiler heating plants the operator has a choice between the operation of one boiler or a combination of boilers to meet the heating needs for a given outdoor air temperature. Under such circumstances the choice of which boiler or boiler combination that should be operated for a particular heating load caused by the outdoor air temperature is not self evident. Thus, typically the boilers will be turned on in a random fashion by the operator to meet the load requirement at hand.
The present invention provides a sophisticated method for determining which boiler or boiler combination in the central heating plant should be put in use depending on the current outdoor air temperature. An apparatus to automatically perform such optimized operation is also provided as well as a method of diagnosis of boilers which require servicing.
2. Description of the Prior Art
Efforts have been made in the prior art to optimize boiler operation and selection in multiple boiler plants. For example, U.S. Pat. No. 4,637,349 discloses a system for controlling central heating boilers of large capacity in which the boiler is switched on and off when the boiler's flow temperature reaches a predetermined maximum or minimum. The boiler flow temperatures are varied dependently upon the outside air temperature in such a manner that as the outside air temperature rises the boiler is switched on at a progressively lower boiler flow temperatures. The result of this boiler cycle controller is to achieve longer boiler cycling. Another example of boiler optimization is set forth in U.S. Pat. No. 4,418,541. There a boiler loading system for a plurality of boilers in a power plant is disclosed. Each of the boilers is continuously monitored for an optimum efficiency change whether for a boiler load increased demand or a boiler load decreased demand. The boiler with the largest efficiency change for a boiler load increase is then selected to satisfy the plant demand. The boiler with the lowest deficiency change decrease is selected where the load demand is for a reduced load. Such a system requires the monitoring of each boiler's fuel flow and load and the establishment for each boiler of an efficiency characteristic function which relates fuel cost to steam flow. None of the prior art methods provide a simple adaptive method or apparatus for selecting and operating optimum boiler or boiler combinations in multiple boiler plants depending on the current outdoor air temperature and historic and current fuel consumption.